1. Field of the Invention
The present invention relates generally to a process and machinery for the plastics extrusion industry, particularly to a removable material hopper assembly for gravimetric blenders, and more particularly for gravimetric batch blenders. The hopper assembly is capable of releasably securing the hopper to a blender, the hopper for storing at least one particulate ingredient and delivering that particulate ingredient with high-precision metering for the blender to, for example, an extruder. A method of using the removable hopper assembly is also disclosed, during which no residual ingredient material is left on the blender after hopper removal.
2. Description of Related Art
Conventional blending devices blend various types of solid particulate ingredients, such as plastic pellets. These devices typically include a number of ingredient hoppers, each of which discharges ingredients into individual metering units. These metering units typically include a metering auger, the rotational speed of which can be varied to control the flow rate of the individual ingredients. The metering units typically discharge, or feed, individual ingredients into some sort of common hopper at independently controllable feed rates which can be varied to produce and control the desired blend of individual ingredients. A metering unit, particularly of a batch blender, may also consist of a gate mechanism, the opening time of which can be varied to control the amount of material fed of an individual ingredients.
One disadvantage of blenders, and in particular conventional batch blenders is difficulty in cleaning. Thorough cleaning of the hoppers is normally required to avoid contamination when changing ingredients, particularly when changing feed material having a different color than what was once held in the hopper. To simplify cleanout of the hoppers and related parts of the blender, it is desirable to removably mount the hoppers so that they may be individually removed. To avoid spillage, each removable hopper should have a shut-off mechanism in the neck of the removable hopper to cut off the ingredient flow through the neck when, and after, the hopper is being removed.
Even without unintended spillage, the removable hopper should limit, and preferably eliminate, residual material being left over from the hopper removal process. Although not technically spilled out from the hopper during removal, material that remains behind on the blender below the shut-off mechanism in the neck of the hopper must nonetheless be separately cleaned away before hopper return.
One attempt at a removable hopper design is disclosed in U.S. Pat. No. 6,057,514 to Maguire. This patent is directed to a gravimetric weigh scale blender with a hopper slidably supported on a frame. The hopper is removably mounted on the frame and horizontally slidably movable with the frame between a first and a second position. The hopper includes a discharge opening located substantially over a weigh pan when the hopper is at the first position.
A metering means, not attached to the hopper, comprising a pneumatic piston-cylinder actuated slide gate combination selectively releases material from the hopper into a mix chamber. A separate shoe is provided that is movable with respect to the hopper. The shoe is orientated above the metering means such that the shoe and slide gate are separated by a distance. The shoe comprises a valve opening in registry with the discharge opening in an open-valve condition, and out of registry with the discharge opening in a closed-valve condition. The shoe presents this valve between the hopper discharge opening and the mix chamber, wherein the shoe is removable with the hopper from the frame.
The blender further comprises a means for mounting the shoe on the hopper for displacement between the open-valve condition and the closed-valve condition, and an operator engaging the shoe for effecting such displacement. The operator is a saddle on the frame abutting the shoe for effecting shoe displacement relative to the hopper when the hopper is moved horizontally with respect to the frame. The saddle is responsive to a horizontal slidable movement of the hopper to position the shoe in the open-valve position when the hopper is at the first position operably mounted on the hopper frame, and to displace the shoe to the closed-valve position when the hopper is slidably moved toward the second position and removed from the hopper frame.
Prior to the Maguire device, it was known to put a valve at the bottom of a hopper to control the amount of material being fed to the blender""s metering means. It also was known to provide removable hoppers with slide gates, and it was known to use a shoe to prevent hopper material spill. More specifically, it was known to place a hopper on a sliding track for removal and to make the shoe on the bottom of the hopper close the bottom of the hopper and removable with the hopper.
What Maguire appears to have provided to the art is a removable hopper design incorporating a sliding gate and a separate removable shoe, wherein the removable shoe has a specific geometry limited to a bottom plate coplanar with the discharge opening of the hopper, the shoe further having upstanding vertical and inclined side flanges slidably engaging vertical and inclined side walls of the hopper, wherein a saddle on the frame is operable to displace the shoe in the plane of the discharge opening in a path parallel to parallel sides of the opening.
Thus, while the Maguire device provides a removable hopper, such removability is at the price of complexity of parts and difficulty in practice. The shoe and hopper are slidably movable in only a very unforgiving and limited way, laterally through the use of a pin residing in a longitudinal slot of the shoe to control the relative position of the shoe when the hopper is movable between hopper open and hopper closed positions.
Further, the Maguire device provides only a limited solution to the problems of hopper cleanout procedures. Although the Maguire hopper is removable, ingredient material remains on top of the slide gate as the shoe and slide gate are separated by a distance. This material remaining between the shoe and slide gate must be manually cleaned upon hopper separation.
In view of the above, it is apparent that there exists a need to provide a simplified assembly enabling removability of a hopper from a frame. Additionally, such a removable hopper should limit or eliminate the residual material that remains after the prior art material hopper is removed from the frame. It is to the provision of such a removable hopper assembly that the present invention is primarily directed.
Briefly described, in a preferred form, the present invention is an improvement over the conventional hopper/blender unit by providing a removable assembly enabling removability of the hopper from the blender. The removable assembly comprises a sealing device to seal off the neck of the hopper during hopper removal from the blender. The same sealing device is also the metering control, regulating material flow rate from the hopper.
As a unit, the invention provides an ingredient hopper that is removable from a blender, wherein the hopper has a metering slide gate that can be used to tightly seal off the bottom of the hopper during the removable operation. The present removable material hopper assembly includes the hopper, a metering assembly and a releasable securing assembly. The metering assembly comprises a metering gate locking pin, the metering slide gate and a metering cylinder. In effect, the metering slide gate both regulates material flow rate from the hopper, and ensures that no residual material will remain on the blender during hopper separation. The metering slide gate slidingly moves along metering gate support guides by the metering cylinder. The metering slide gate can be locked against movement by the metering gate locking pin.
Further, a releasable securing assembly is provided that simplifies removability through the use of a quick release pin and retaining brackets on the top plate of the blender. The releasable securing assembly further comprises a tongue and locking groove subassembly that cooperate to align and lock the hopper on the top plate. The quick release pin can be slidably engagable through the bottom portion of removable hopper and corresponding retaining brackets. The tongue extends from the bottom portion of the hopper and is slidably engagable within a corresponding locking groove of a divider plate of the top plate. Such a design is distinguished from the prior art in that present blenders with removable hoppers include a sealing element and a shoe, both elements separate from the hopper and the blender.
The present invention""s novel use of the metering gate as the shut-off valve during hopper removal necessarily eliminates the prior art disadvantage of residual hopper material being left on top of the metering gate, which residual material must be cleaned before the hopper can be placed once again on the frame. If the residual material is not separately cleaned away, the residual material will be left to mix with any new and different ingredient placed in the hopper.
Further, the novel releasable securing assembly makes hopper removal quick and easy.
Thus, an object of the invention is to provide an improved hopper/blender assembly. Another object of the present invention is to provide an improved removable hopper that is easy to lock and unlock into operational position. Yet another object of the present invention is the provision of a method of hopper removal that eliminates residual material left upon hopper separation. These and other objects, features, and advantages of the present invention will be more apparent upon reading the following specification in conjunction with the accompanying drawings.